The present application relates to a transmitter, a receiver, a signal transmission system, a signal transmission method, which are applicable to a three-dimensional signal transmission system that employs a serial digital interface of a dual-link connection to transmit a two-dimensional image signal and depth information for representing a three-dimensional image. Specifically, when a three-dimensional image signal including a two-dimensional image signal and depth information of the two-dimensional image signal is transmitted to a receiver using a two signal transmission lines, signal separation of the two-dimensional image signal is performed, one signal-separated part of the two-dimensional image signal is transmitted to a first signal transmission line, and the other signal-separated part of the two-dimensional image signal is combined with the depth information and then transmitted to a second signal transmission line, one link of the serial digital interface of dual link connection can transmit the two-dimensional image signal S11 and the other link thereof can transmit the two-dimensional image signal and/or the depth information thereof.
In recent years, televisions have become thinner and the screens thereof have become finer and larger and, as a next paradigm shift, three-dimensional image representation has been intensively studied. As a display form of a three-dimensional image signal using binocular disparity, typically, there are two different display forms. A first form is to combine a two-dimensional original and the depth information thereof and a second form is to combine a two-dimensional image signal for left vision and a two-dimensional image signal for right vision.
In the first form, depth information is extracted from a two-dimensional image signal and signal processing in response to the extracted depth information is then carried out on the two-dimensional image signal to allow a viewer to recognize a three dimensional signal. In the second form, a parallax difference is previously provided between a two-dimensional image signal for left vision and a two-dimensional image signal for right vision to allow a viewer to perceive a depth corresponding to the parallax difference and recognize a displayed image as a three-dimensional image.
As a transmission method for two-dimensional image signal, the SDI (Serial Digital Interface) standard has been widely used for professional uses in the broadcast industry and so on. The SDI standard includes two different standards, one is the SD-SDI standard used for transmitting a video with a standard image quality and the other is the HD-SDI standard for transmitting a high definition image. In addition, the HD-SDI standard includes two different types, a single link connection and a dual link connection.
A signal transmission technology using a single-link connection interface is disclosed in Bit-Serial Digital Interface for High-Definition Television Systems (SMPTE STANDARD 292M-1998). According to this signal transmission technology, for example, it is possible to transmit a 10-bit image of YCbCr422 format with a horizontal resolution of 1920 pixels and a vertical resolution of 1080 lines at a rate of 30 frames per second in progressive form or at a rate of 60 fields per second in interlace form.
On the other hand, a signal transmission technology using a dual-link connection interface is disclosed in Dual Link 292M Interface for 1920×1080 Picture Raster (SMPTE STANDARD 372M-2002).
In this signal transmission technology, for example, it is possible to transmit a 10-bit image of YCbCr444 format with a horizontal resolution of 1920 pixels and a vertical resolution of 1080 lines at a rate of 60 fields per second in interlace form. Alternatively, it is possible to transmit a 10-bit image of RGB444 format with a horizontal resolution of 1920 pixels and a vertical resolution of 1080 lines at a rate of 60 fields per second in interlace form.
In relation to a typical technology for transmission of three-dimensional image signal, furthermore, a transmission method, a transmitting-side apparatus, a receiving-side apparatus for three-dimensional image information are disclosed in Japanese Unexamined Patent Application Publication No. 2007-166277, particularly in page 10 and FIG. 1 of this document. According to this transmission method for three-dimensional image information, when a three-dimensional image signal is transmitted from a transmitting-side apparatus to a receiving-side apparatus using an interface capable of transmitting digital signals, such as those of DVI, the interface is provided with a function of transmitting 8-bit image signals corresponding to the respective RGB colors and this interface is used for transmission of 6-bit signals of the respective RGB colors and 6-bit depth information thereof.
In the method disclosed in such a patent document, it is noted that the low 2 bits of each of RGB colors is assigned to the bits of depth information without changing a bit rate used for the transmission. Such configurations of transmitting-side and receiving-side apparatuses lead to the transmission of a three-dimensional image signal without changing the maximum number of representable colors of the original two-dimensional image.
According to the above patent document, even if the above three-dimensional image signal is received by the display apparatus which can only display a two-dimensional image signal, the low 2 bits of each of RGB colors are not recognized as depth information but only recognized as RGB information. Thus, a difference in color of unrecognized bits is hardly recognized by a viewer.